Gamma detection devices are used for locating radiation concentrated in animal tissue. The use of gamma detection devices is rapidly becoming the standard of care for surgical management of melanomas and increasingly for breast tumors. Gamma detection devices typically include standard (whole body) gamma cameras and hand-held non-imaging gamma detection probes, and are increasingly used for axillary staging in conjunction with removal of the primary tumor. Hand-held non-imaging gamma detection probes may also be referred to as non-imaging gamma detection probes, gamma probes, or non-imaging probes.
The presence or absence of regional lymph node involvement often determines the staging and treatment of malignant tumors. Lymphoscintigraphy, which typically allows monitoring of selected regional lymphatic drainage, is increasingly being used to determine which lymph node basins serve the diseased tissue, e.g., a tumor. During lymphoscintigraphy, a sentinel node concept is typically applied to estimate the extent to which a cancer has spread. The sentinel node concept is based on the observation that metastatic cancer cells travel primarily through lymph drainage to spread the cancer throughout the body. The sentinel node is defined to be the first lymph node downstream from the tumor.
Studies have indicated that, if there is no sign of malignancy in the sentinel node, the probability that cancer has spread is very low, and it is typically not necessary to remove the downstream lymph nodes, which had previously been a routine procedure during the treatment of breast cancer. The removal of downstream nodes (often more than 15 such nodes) has left many patients without adequate drainage for the lymph, and has led to serious edema and swelling, which often lasts many months to years. Thus, the use of the sentinel node concept to remove only the sentinel node typically reduces cost, morbidity and mortality, and provides equivalent or superior accuracy to axillary lymph node dissection.
In practice, a colloid labeled with 99mTc is generally injected in the region just outside the tumor, and a set of scintillation camera images are typically taken using a standard (whole body) gamma camera. These images typically show the migration of the colloid from the area of the tumor to the sentinel node and eventually to other nodes downstream from the tumor. Non-imaging gamma detection probes typically are then used at the time of surgery, both before and during the surgical process, to further localize the implicated nodes. The systems that include non-imaging gamma detection probes generally have an audio output that increases in sound level and/or frequency as the count rate of gamma rays increases. They may also display the number of gamma rays detected.
There are a number of shortcomings associated with using the non-imaging gamma detection probes. For example, the non-imaging system typically only registers the aggregate count rate and generally has no capability to distinguish localized concentrations of radiation from uniform ambient background, and typically has a very limited capability to distinguish between multiple local concentrations of radiation that are in proximity to one another. For another example, the non-imaging gamma detection probes typically are used to localize radiation to an area no smaller than its size, and thus the non-imaging gamma detection probes are typically kept relatively small to enhance their ability to localize radiation. Thus, it typically takes a long time to scan the area including the lymph basin and the area surrounding the injection.
Because of these and other shortcomings, there typically are a number of ambiguities associated with current modes of detecting the gamma ray or providing an output to indicate the detection. These ambiguities are typically associated with but not limited to: distinction between the injection site and nodes that are in proximity to the injection site; distinction between the sentinel node and secondary nodes; distinction of the sentinel node from activity along the path of migration of the injected colloid; and three-dimensional localization of the sentinel node.
Therefore, there is a need for a hand-held gamma detection probe that can reduce the ambiguities and facilitate the process of locating the sentinel node and distinguishing it from other sources of gamma ray radiation such as the injection site, other nodes, background, radiation due to scatter, etc.
One embodiment of the present invention is an imaging probe system for locating and examining the distribution of radiation concentration in animal tissue. The imaging probe system includes a portable imaging probe for detecting the distribution of radiation and a computer for processing the signal arising from the detected radiation. The imaging probe system also includes an audio output device that indicates the presence or absence of one or more radiation sources in the field of view (FOV) of the portable imaging probe. The frequency of the audio output may be varied in proportion to the count rate, and the modulation of the frequency, volume, and/or phase of the audio output also may indicate the presence of a focalized xe2x80x9chot spotxe2x80x9d of radiation distinguishable from its surrounding, or more than one source in the FOV. The imaging probe system is also capable of providing images of gamma ray radiation distribution in the FOV with or without the audio output. The imaging probe system is capable of identifying and imaging gamma ray distributions both pre-operatively, e.g., for pre-surgical staging, as well as intra-operatively, e.g., in the operating room.
Another embodiment of the present invention is an imaging probe system having first and second portable imaging probes disposed one from the other at a known angle. The first and second portable imaging probes are used to generate X, Y and Z coordinates of a radioactive node. The X, Y and Z coordinates are used for three-dimensional localization of the radioactive node.
Yet another embodiment of the present invention is a portable imaging probe to assess a distribution of radiation concentrated in animal tissue. The portable imaging probe includes a collimator to direct rays of radiation such as gamma rays. The portable imaging probe also includes an imaging sensor to detect the rays of radiation. The imaging sensor can be a scintillator or it can be an energetic particle sensitive solid state detector. Different collimators with different aperture sizes, different number of chambers, and different chamber wall configuration, e.g., pin hole, diverging or parallel, can be used to vary spatial resolution, sensitivity and field of view.
Yet another embodiment of the present invention is a portable imaging probe that has a beta detection sensor in addition to a gamma detection sensor.
Yet another embodiment of the present invention is a method of assessing a distribution of radiation concentrated in animal tissue. The distribution of radiation is measured using a portable imaging probe. The measured distribution of radiation is processed to identify local concentrations of radiation. The local concentrations of radiation are indicated to the user through audio signals, images or a combination of the audio signals and images.